Hmmm. Phil - you need to clean up your article. ;-) As you have described the wheel,

"...a 6"-wide wheel should protrude 3-1/2" inboard and 2-1/2" outboard...."

...it will indeed have 0.5" positive offset, not 1.0". In order for a 6" wide wheel to have 1.0" positive offset, the inboard and outboard measurements would have to be 4" and 2", respectively.

Paul - FWIW, this brings up another trap for many folks, especially when talking about backspace measurements; the possible misuse of the term "rim width". Technically, rim width is an inside measurement taken between the (more or less vertical) bead seats of the rim. Many use this term more loosely, to describe the outside measurement that is the overall width of the wheel... the distance as measured from one outermost edge of the wheel to the other. This means a 15x6" wheel might actually measure 7" in width. To further confuse the issue, the overall width of various 15x6" wheels can vary significantly, depending on type... cast aluminum vs stock steel wheels, for instance. So be very careful when comparing "offset" and "backspace" between dissimilar wheels.

Gary L

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1971 142E ITB racer, 1973 1800ES, 2002 S60 T5